Hi I have been meaning to post about this machine for quite a while. I am now at a point where I believe the problem is a leak into the torque converter housing causing no lube pressure until held in a stalled condition for a while. Ill give the background story first as it will be interesting reading for some I hope and it might help someone else out that is having repeated transmission pump failures, as this was the initial problem. The cause of the failures seemed to get overlooked multiple times by multiple mechanics including a Cat dealer as best as I can tell from my detective work. Cat 966G AAH00320 This loader has had transmission heating problems ever since I purchased it a few years ago. Just prior to purchasing it the transmission had been stripped down, inspected and resealed. Apparently a new torque converter was installed at that time and a new transmission pump (second pump with this owner). I know this was all done as the parts were purchased from a supplier that I also use and they backed up everything I was told. Apparently the guy purchased it out of the auctions and put it to work finding that the transmission would overheat. They did the troubleshooting (he was a mechanic IIRC) and they found the transmission pump was stuffed. They replaced this with an aftermarket one and put it back together. Went back to work and was still getting hot. So at this point they decided to pull the transmission out and overhaul it. On disassembling it, I am told, they found that everything measured up like new inside in the transmission section. They found the transmission pump was stuffed again and when they got to the torque converter it had cracks in the impeller. They got a new pump under warranty and sourced a second hand impeller. When the impeller arrived it was found to have issues, so they had to get a new one and IIRC they got a full new torque converter. They then resealed everything and reassembled it. Apparently it then went back to work for a while to make sure that everything was good (or so I was told) and then it went up for sale. The guy was doing some trading of machines and it seemed to all check out with the parts that had gone into it. I tested it a bit in his yard and it seemed good to me and a mate who is a mechanic that came with me.... knowing everything i have learnt since about transmissions with the problems I have had, I would now pressure test the transmission on a machine prior to buying. I would recommend this to anyone reading!!!! I know most experienced people on here would know this but for anyone that doesn't I think it is a must if you can. So back to the story. We got it home and it went straight to work desilting the dam at our house. It was the middle of summer and if it was going to have problems this would find them. The transmission after a few hours would be right up the top of the gauge even if trying to nurse it. I called the bloke and he thought it might be the pump again. I purchased a set of cat gauges and went though everything else I could think of on the cooling side. I adjusted the main pressure valve and eventually replaced it because it had a bit of scoring. With adjustments and fine tuning I got it usable for a while but the Trans lube pressure was always around the minimum and it always ran pretty warm when working hard so you had to nurse it. I needed to try and make a few dollars so I nursed it along over winter till it got hotter and then I got to the point that I wasn't happy to keep going any longer. I purchased a genuine cat pump (thinking the aftermarket pump could be the culprit) and decided that I was going to swap pumps and inspect the old one at the very least. If it wasn't the pump it had to be internal leakage as far as I could tell. When we separated the other pumps off the trans pump something wasn't right, but I found the culprit later after pulling the trans pump apart and seeing the damage. I can post photos if people are interested, but what i found was the gears in the trans pump had cut the hell out of the back side (closest to the engine) of the pump housing. It had then seized and spun bearings on the free wheeling side shaft. Very little wear on the front side of pump housing and the back side looked like it had been milled by the gears. I went to the implement pump and found the sliding coupling between the two pumps was locked to the implement pump shaft. I needed a puller to remove it. So what had been happening was a new trans pump would be fitted, it would be preloaded into the back of the housing when installed. When started up I assume it would mill out the back of the new pump and have the same symptoms as before it was fitted in very short order. I found a tag from a cat dealer on top of the transmission so I called the dealer to find out if the coupling was indeed supposed to slide freely as I suspected and to find out about the overhaul. The coupling was absolutely supposed to slide freely and I managed to talk to the guy at the rebuild center that actually did the overhaul a few years before. He had notes on the transmission but never had anything to do with the actual machine. He did find its history though and that is when we discovered the rest of the story. So the story actually started a few years before and before the trans was rebuilt.... apparently Cat fitted a new implement pump to the machine... not long after that they fitted a new transmission pump.... not long after that they pulled the trans out and sent it to the rebuild centre for an overhaul and another new pump. We agreed we were on the right track with the implemnet pump and so he did some more digging and found a service buliten that came out about the time the pump was fitted to the machine. It said there were defective shafts in a run of those implememt pumps and they were a recall item. It was way past the time to return it by that stage but at least we had the culprit, cause, and the full story. I believive the story to be, in short form... 1: new implement pump 2: that caused the trans pump to fail so a new one was fitted 3: it a was still having transmision problems so they rebuilt the transmision and fitted a second new trans pump 4: it was still having problems and no one could work it out (it had gremlins), so they put it in the auctions for some else to deal with. 5: The guy before me got it, had problems and found the trans pump buggered so fitted the 3rd pump 6: still had problems so eventualy pulled the trans out, found it like new, found the TC issues (I'd say from heat damage) so replaced that and found the destroyed pump again so replaced that with pump no.4. 7: Tested it and found it was still getting pretty hot (diagnosed with gremlins again), but hoped that it would outlast the tail-lights warranty. 8: this was where I came in. In his defence the guy did offer to help me try and fix it as soon as I started having problems but he let slip that it was actually still getting hot, when he had told me when I purchased it that it was running perfectly and all was fixed. So I figured I didn't want to deal with him if I couldn't trust him. No pumps were available for weeks via Cat, so I very carefuly with a dremel and small stone wheel ground the gap on the teeth of the spline on the shaft down by hand till the point that the coupling would just slide freely. I had nothing to loose so thought it was worth a shot. I got it to work after many careful hours, so we installed the new trans pump and put everthing back together. The pressures needed resetting but everthing was in spec finaly. Working hard pushing a stickrake or other work, it would get up to 3/4 on the temp gauge and stop there. All was good then for about 600hrs untill a job this summer. I will start a new post because that is the end of my novel, so story time is over, I hope people find it an interesting read....
So now to the current problem, which I expect is the result of heat caused by the last trans pump failure finally . Over winter I suspected it was getting a bit warm a couple of times, then it had a break from hard work till summer and it will now overheat quite easily once warmed up and wont cool off. The moment the torque converter starts loading up it climbs rapidly and doesn't really want to come back down. Pressure testing showed there is no lube pressure showing under the test parameters. If you hold it in a stalled condition for a bit the lube pressure actually starts rising. I'd have to check the videos I took of the pressure gauge but i think the Torque converter outlet pressure is on spec but when its stalled the inlet pressure drops bellow the outlet. The oil level in the sight glass also drops out of sight when it gets stall tested. My theory is I have a leak that floods the torque converter housing and it isn't letting much oil go through the cooler and to the trans lube circuit. So I am at the point that I believe the transmission has to come out again and there will be a blown seal somewhere in the converter so it needs to be resealed. I am very tempted to send it to the Cat dealer but they want to completely overhaul it and it is going to cost a lot. At least it will come back with a warranty and I haven't had time to do anything with it for a couple of months and I need it going. What I want to know is, if I decide to do it my self, can you split the trans off the engine in the chassis? One manual I have looked at says pull the engine with it. Also If anyone has any ideas that might save me pulling it out I am open to suggestions!!! I can find all my videos from pressure testing and post results if more data is wanted before advise. Thanks for any help offered and I hope my story time above might save some grey hairs for someone else if they run into a similar problem
I have seen this problem before with premature pump failure due to worn splines creating pressure on the transmission pump drive gear. The sad part of this is that they replaced the whole torque converter over a bad impeller. The aftermarket torque converters are a cheap alternative but they are lacking in quality in my experience. The problem is now you have to buy all the torque components to get back to cat original. The trans should come off the engine in frame and come out on its own if you remove the cab first. You will need to block the back of the engine up usually can block it on the rear diff housing.
Yes funny part with this one was the splines were like new, just slightly oversized. I’ll see if I can find out if the whole converter was changed… the more I think about it the more I think I was told it was genuine cat, so might have just been the impeller. I’m a bit hazy on that but I think I remember the parts supplier saying that they had to get the guy a genuine one as aftermarket wasn’t available at the time. This is where Cat is a bit worried about just resealing everything. The first quote for Reman exchange fitted was $100K, new quote after I said no, is now $65k for exactly the same. Must have been mine pricing the first round. It seems like a waste to do a complete rebuild again when the last Cat one was only about 4000hrs ago IIRC and it was resealed about 1000hrs ago. But 500hr warranty and interest free finance for 2 years are worth considering. I’m not getting time to do it myself so I’m coming to terms with having to paying someone else to do it
I know what you mean. Sometimes you just have to take a hit and move on. It’s too bad cat never has to shoulder some of the cost for a problem they clearly created.
Yeah it’s just a lot bigger hit than I was hoping for haha. You are right though!! I’m having a look at a 962H today a long way from home as an upgrade for my 966C. If any of the Australian readers are interested in a 966C and a D6C let me know. If this works out it will give me a machine to use while the 966G gets fixed. Im going to try employing a driver I think so I can try to keep them busy to pay for the repairs. There is also a 924H but I worry it might be a bit small. Have you had any good or bad experience with 962H (11,500hrs) or 924H (3,600hrs) machines?